The instant invention relates to a flange connector used for joining of ducts having generally rectangular cross-sections, especially in high pressure air duct systems.
Such flange connectors are especially designed for use in assembling and anchoring the various sections of air ducts. As mentioned, the duct sections are normally rectangular and consist of sheet metal with four corner folds. To reduce the propagation of sound which is normally generated by air conditioning or ventilating units attached to the duct, it is common practice to insert a vibration damper in the form of a flexible connector between two duct sections being joined.
Such a flange connector is described in German patent publication DE-PS No. 23 13 425 which shows a frame made of angle bars attached to the front end of a duct section so that the two mutually perpendicular flanges of the angle bars run parallel and perpendicular to each wall of the duct respectively. The flanges also are designed to receive and anchor a rectangular corner fitting, which is used to connect two bar members to each other. The frame is then fixed to the front ends of the duct sections and can be flanged against a similar frame that is attached to the adjacent duct section whereby a rubber seal or the like is inserted between the two opposing flanges in order to eliminate air leaks and to inhibit transmission of sound vibrations.
These known angular bars, however, are costly because they have essentially double walls for each flange which in principle results in four walls. Considering that such angular bars meant to stabilize duct sections are normally manufactured out of steel, it is obvious that the abovementioned construction leads to high material usage and therefore to enormous material costs.
On the other hand, since the thin sheet metal walls of the duct sections do not have the generally required structural stability, a flange connector made of such angular bars lends rigidity to the duct. Therefore, it is not possible to eliminate the couplers and their attendant cost altogether.
Corner fittings used to join the angle bar members to a frame generally feature pin-like lugs which extend perpendicular to one another and which are adapted to be inserted between the double walls of one flange of the angular bar that extends perpendicular to the respective duct wall. These corner fittings are essentially punched out of sheet metal and would generally not allow the desired sealing effect at corner points between two adjacent duct sections. Therefore, more often than not, an elastomeric compound must be applied to the joint to establish an adequate seal which will avoid energy losses through air leaks.
Another disadvantage of such flange connectors is the difficulty in joining it to flexible connectors having flexible wall material, such as coated fabric, which is manufactured differently than the ones used for solid duct walls. The sealing problems associated with flexible material are just as severe. Finally, it is common practice to use a wider width of flange for air ducts of larger cross-sections and a narrower flange width for smaller ones. This necessitates the manufacturing and stocking of various sizes of angular bars which, in turn, increases cost.